The dimmability of light-emitting diodes (LEDs) offers lighting designers great flexibility in illuminating an indoor environment. However, even for experienced lighting designers, it is not easy to achieve both comfort and energy efficiency using large-scale lighting systems. To improve this situation, in this paper we propose the use of a quantitative human perception model for an illuminance distribution in an indoor environment. Based on this model, we can optimise the dimming levels of the LED lighting system given the positions and preferences of users. Enhancing user satisfaction and reducing energy consumption are jointly taken into consideration.